1. Field of the Invention
The present inventions relate to at least one zoom lens and at least one image pickup apparatus including the same. The present inventions are suitable for image pickup apparatuses that use an image sensor, such as, but not limited to, a digital still camera, a video camera, a monitoring camera, and a broadcasting camera, and an image pickup apparatus, such as a camera that uses silver-halide film.
2. Description of the Related Art
Image pickup apparatuses that use a solid-state image sensor, such as a digital still camera and a video camera, have recently increased in performance and decreased in size. Thus, zoom lenses for use in such apparatuses are required to have a small overall lens length and a large aperture.
Japanese Patent Laid-Open No. 2012-47814 discloses a zoom lens including, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, a fourth lens unit having positive refractive power, and a fifth lens unit having negative refractive power.
The zoom lens disclosed in Japanese Patent Laid-Open No. 2012-47814 has an aperture stop between the third lens unit and the fourth lens unit.
To obtain a high-resolution image-pickup optical system, it is generally important to appropriately set the configuration of lens elements disposed at the object side with respect to the aperture stop and the configuration of lens elements disposed at the image side with respect to the aperture stop in the image-pickup optical system. Inappropriate configurations thereof will make it difficult to obtain a large-aperture zoom lens in which an increase in the effective diameter of a front lens and an increase in the diameter of an aperture stop are reduced. In particular, excessively strong refractive power of a second lens unit makes it difficult to reduce the occurrence of field curvature in all zoom ranges.